1. Detailed Description of the Invention
The present invention relates to a method of preventing deformation of a lead frame during a plating process.
2. Description of the Prior Art
The lead frame has to-be-plated portions including die pads on which the pin tips and chips are mounted, and these portions are plated with a noble metal etc. After the lead frame is subjected to surface treating process, mainly the plating treatment, it is subjected to assembly process including wire bonding, resin molding, etc. to be finally fabricated into electronic package parts.
The treatments to be applied to the lead frames in the respective processes are carried out as follows. A plurality of lead frames are forwarded at one time on a mechanical transfer line employing a roller mechanism or a chucking mechanism, and they are automatically treated by a plating unit (see, e.g., Japanese Unexamined Utility Model Publication No. 60-105658) and an assembly unit arranged on the mechanical transfer line.
Recently, there is a tendency toward thinner and multi-pin structure lead frames, so that the lead frames are liable to undergo deformation during travelling on the mechanical transfer line. Accordingly, the molding areas excluding the to-be-plated portions are provided with adhesive tapes or resin films to cover the area after completion of the surface treating process so as to prevent such deformation of the lead frames.